There is a technical desire to selectively separate a specific substance (gas or the like) from a mixture of a plurality of substances (gas or the like) at a molecular level, and, as a filter responding to the desire, there are generally known ones each employing polysulfone, silicon, polyamide, polyimide, or the like as a separation membrane.
However, since these have separation membrane made of polymer resin, these inherently have a problem that target substance for separation is limited because the membrane is easily altered and deteriorated when an organic solvent is contained in the mixture serving as the target substance for separation.
Therefore, in recent years, as a filter excellent in chemical stability and thermal resistance, a complex where a carbon membrane as a separation membrane is formed on a porous body (a porous substrate) had been proposed.
For example, in Patent Document 1, there is proposed a molecular sieve carbon membrane having a carbon content of 80% or more, presenting a large number of pores having a pore diameter of 1 nm or less, and adhering to a surface of a coating layer of silica sol, alumina sol or the like formed on a surface of a ceramic porous body having a porosity of 30 to 80%. This molecular sieve carbon membrane can be obtained by applying a liquid thermosetting resin (phenol resin) to form a polymer membrane, followed by a thermal treatment at 550 to 1100° C. under a non-oxidizing atmosphere.
FIG. 3 is a schematic view showing a cross section of such a molecular sieve carbon membrane (separation membrane complex). The molecular sieve carbon membrane 3 shown in FIG. 3 has a porous body 31 and a carbon membrane 36 formed on a surface of the porous body 31, and a sol layer 35 (a coating layer) of a silica sol, alumina sol, or the like is formed on the surface of the porous body 31, with a carbon membrane 36 adhering to the sol layer 35.
Patent Document 1: JP-B-3647985